Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr₃

Abstract

Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching Cu II -X modes in the equatorial plane, were found in the ranges 247-288 cm −1 for X = Cl, and 173-189 cm −1 for X = Br, while the low-wavenumber stretching modes for the weaker axial Cu-X interactions varied considerably. The tetrahedral coordination for Cs 2 CuCl 4 and Cs 2 CuBr 4 leads to somewhat lower Cu-X symmetric stretching wavenumbers, 295 and 173 cm −1 , respectively. The assignments of the copper-ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged Cu-X stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn-Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer-sphere cations. Force constant ratios for terminal and bridging metal-halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M 2 X 6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr 3 (K 2 Cu 2 Br 6 ), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu 2 Br 6 ] 2− complexes held together by weak axial Cu-Br interactions.

Structures, Bonding and Sensor Properties of Some Alkaline o-Phthalatocuprates

“…Some increase in C-O stretching force constants reflects a lower polarization effect of copper ions compared to hydrogen. As for copper-oxygen bond strengths, the results are rather similar to those for another complex with oxygen-donor ligands [26]. It should be mentioned that no obvious effect of outer-sphere cations on metalligand bond strengths is observed in o-phthalatocuprates, in contrast to that found in halide complexes [26,27].…”

“…As for copper-oxygen bond strengths, the results are rather similar to those for another complex with oxygen-donor ligands [26]. It should be mentioned that no obvious effect of outer-sphere cations on metalligand bond strengths is observed in o-phthalatocuprates, in contrast to that found in halide complexes [26,27]. The polymeric structure of complexes and large size of ligands leads to the smoothing of the effect of polarization ability of outer-sphere ions.…”

Multi-Modal Compositional Analysis of Layered Paint Chips of Automobiles by the Combined Application of ATR-FTIR Imaging, Raman Microspectrometry, and SEM/EDX

“…The Al and Si X-ray peaks for layers #2 and #3 suggest the presence of an aluminosilicate mineral, but its speciation based on the ATR-FTIR spectra is not feasible because of its low content (Figure 8a). Small Cu and Cl X-ray peaks for layer #3 suggest the presence of a small amount of CuCl 2 , but it was difficult to detect by RMS (Figure 7) [59].…”

Instantaneous gelation of a new copper(ii) metallogel amenable to encapsulation of a luminescent lanthanide cluster

“…Furthermore, a decrease in the N-H stretching vibration and a band at 225 cm À1 that correlates with the d(Cu-Cl) vibration of a coordinated copper centre in the Raman spectrum are consistent with the proposed structure. 13 The nanoscale morphology of the dried gel was next investigated by SEM, which confirmed the presence of rod-like nano-fibres (Fig. 3).…”